A need has arisen for window assemblies with fixed but removable upper sashes. Removal of the upper sash is necessary for two primary reasons. One, if the window is on an upper story of a building, the sash needs to be removed to facilitate cleaning, access to a fogged insulated glass unit, or convenient replacement of broken glass. Secondly, contractors frequently frame up a structure, close in the walls and install the windows prior to construction of interior space. The reason for this is to limit exposure to the weather and often for bank interim financing purposes where disbursement of funds is based on the stage of construction. Consequently, the exterior of a house is often substantially complete before drywall is carried in for installation on multi-floor structures. Drywall is often brought in through the windows. Windows where the upper sash is not removable or where there is a fixed meeting rail attached to the jambs between the upper and lower sashes create a problem for the building contractor because entry of drywall and other large items is difficult.
U.S. Pat. No. 2,509,582 is an example of a window assembly with a removable upper sash. In this design, the upper sash is supported by a projection attached to the upper sash that fits into a section of the frame jamb. This approach permits deformation and bowing of the jamb. A defective jamb allows air to enter in between the window sash and the jamb, thus necessitating an expensive repair.
U.S. Pat. No. 4,831,778 is another example of a window assembly with a removable upper sash. In this design, a projection affixed to the upper sash fits into a notch in the frame jamb. This design is deficient in that, among other things, the notch does not prevent movement of the upper sash in the horizontal direction, thus the jambs may rotate.
Therefore, a need has arisen for a new method and apparatus for installing a window assembly that overcomes the disadvantages and deficiencies of the prior art.